Error Logs & Apollo 11: One Giant Step for Risk Management

The recent passing of Neil Armstrong is more than the loss of a hero, but a lost connection to one of humanity’s greatest achievements. The Apollo 11 mission brought people together around TVs and radios worldwide to share in what truly was “one giant step for mankind,” inspiring hope and the realization that anything was possible. The mission is also a shining example of a large-scale high risk technology project.

Although Neil Armstrong is the hero of the Apollo 11 story, the planning, management, complexity and technology for the mission is often overlooked. Many don’t realize that if it were not for testing and assessing risks associated with the failure of the Apollo Guidance Computer (AGC) and other systems the lunar landing would not have been a success.

Just as the Lunar Module was descending on the moon its guidance computer appeared to fail and was spitting out cryptic error messages that the astronauts could not understand, consisting of “1201” and “1202” errors. The error messages indicated that the AGC system was being overloaded. However, the ground crew had run into the same errors during a simulation just a few weeks prior to the mission. The software was designed with priority scheduling and they knew that the system would automatically recover and continue to run critical guidance and control functions even if it was not displaying radar information to assist Armstrong in the landing of the craft.

The ground crew determined it was still safe to land the craft and they gave the “Go” command to continue with the mission and Armstrong landed the craft without the assistance of the guidance display. However the Eagle’s boosters controlled by the guidance system continued to function as the ground crew predicted without which Armstrong would not have been able to control the craft. The fact that the ground crew could understand and decipher the error messages from the ACG played a key role in the success of the mission.

It was only by preparing for failures that the Apollo 11 mission was a success. The development of the Apollo Guidance System computers are a technical achievement in themselves, with levels of quality assurance and environmental controls unheard of at the time and something we can still learn from today. With the risk of failure being an aborted mission and the potential death of astronauts, assessing the risk of all the things that could go wrong paired the unknown variables of landing an aircraft on the moon, the level of planning and management was astronomical (pun intended).